Basic viewer app in Arcgis.com online doesn't update legend

When viewing a map in the Basic Viewer app in ArcGIS.com online, the legend only displays the layers that are turned on initially. If you turn off layers or turn on additional layers, the legend does not update to reflect this. The legend appears to now be just a static legend of initial layers. It used to work properly (dynamically) when I last checked a few months ago. Did something change and is there some new setting for this?

The Basic Viewer (and other Configurable Apps) will actually update the legend but only after you zoom in or out. So when you turn on/off layers, the legend will not update until you zoom in/out. Would be nice if they updated immediately like Web AppBuilder apps.

I setup a quick test to try and reproduce the issue with the JSAPI and wasn't able to do so. Is your web map public? If so can you send me the web map id or try replacing the existing id in the sample below with yours and see if its reproducible?